Add AuthenticationClass::resolve (#432)

## Description

*Please add a description here. This will become the commit message of the merge request later.*

Author: sbernauer

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- Add `AuthenticationClass::resolve` helper function ([#432]).
+
+[#432]: https://github.com/stackabletech/operator-rs/pull/432
+
 ## [0.22.0] - 2022-07-05
 
 ### Added

src/commons/authentication.rs

@@ -1,9 +1,12 @@
-use serde::{Deserialize, Serialize};
-use strum::Display;
-
-use crate::commons::{ldap::LdapAuthenticationProvider, tls::TlsAuthenticationProvider};
+use crate::{
+    client::Client,
+    commons::{ldap::LdapAuthenticationProvider, tls::TlsAuthenticationProvider},
+    error::Error,
+};
 use kube::CustomResource;
 use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use strum::Display;
 
 #[derive(Clone, CustomResource, Debug, Deserialize, JsonSchema, PartialEq, Serialize)]
 #[kube(
@@ -45,3 +48,14 @@ mod test {
         assert_eq!("Tls", tls_provider.to_string())
     }
 }
+
+impl AuthenticationClass {
+    pub async fn resolve(
+        client: &Client,
+        authentication_class_name: &str,
+    ) -> Result<AuthenticationClass, Error> {
+        client
+            .get::<AuthenticationClass>(authentication_class_name, None) // AuthenticationClass has ClusterScope
+            .await
+    }
+}